The present invention relates to novel electron beam apparatus and methods for controlling the point upon a target surface at which an electron beam will impinge and, more particularly, to a matrix lens and fine deflection system for determining the sharpness of focus and the exact impingement position of the "spot" of an electron beam on a target in an electron beam focussing and positioning system.
Modern data processing requires high capacity, random access memory of extremely high bit storage density, which memory must permit rapid data storage and retrieval. One advantageous memory device utilizes an electron beam focussing and positioning system of the type having a coarse deflection system for causing the electron beam source to be presented to a selected one of a plurality of electron lenses arranged in the form of a two dimensional matrix, with a second, or fine, deflection assembly for focussing the beam passing through each single lenslet on a desired specific point of a target structure. A system of this type is disclosed in U.S. Pat. No. 3,534,219, issued Oct. 13, 1970 to S. P. Newberry, the entire disclosure thereof being incorporated herein by reference. Additionally, the extremely fine (substantially microscopic) spot size and the rapid repositioning ability of such an electron beam deflection system can be utilized for conventional purposes for which cathode ray tubes have long been used and, furthermore, for such diverse processes as welding, etching photomicrographs for the production of high density integrated circuits and the like.
The dual-stage (coarse and fine deflection) electron beam control system is particularly advantageous in that the electron beam is finely focussed upon any precisely controlled point upon a relatively large surface area target with the finely focussed beam being movable between any two points thereon in highly precise manner and in an extremely short time.